1. Technical Field
The present invention relates to an optical output controller and, more particularly, to an optical output controller for a laser light source employing a wavelength conversion device for use with a display and a method for controlling the same.
2. Background Art
A laser light source device employing a wavelength conversion device is required to maintain the wavelength conversion device at an optimum temperature, in order to maximize the optical output outputted from the wavelength conversion device. Such a wavelength conversion device has a mountain-shaped temperature characteristic which has a temperature at which the optical output is maximized. The temperature, at which the optical output is maximized, is referred to as “optimum temperature”. Also, the optical output is decreased at higher and lower temperatures than the optimum temperature. The optimum temperature is determined by the characteristics of the wavelength conversion device itself and by the wavelength of the inputted laser light, and the like. Accordingly, if the temperature of the wavelength conversion device is fluctuated or the wavelength of the inputted laser light is varied, the optimum temperature is changed.
To cope therewith, conventionally, the temperature has been varied for determining a temperature at which the optical output is maximized, in search of an optimum temperature, as described in Japanese Patent Laid-open Publication No. 10-20351. Operations for gradually varying the temperature, detecting the optical output at the time and comparing the detected optical output are repeated, such that a temperature, at which the amount of light is maximized, is found and the found temperature is set as an optimum temperature. The optical output may be continuously maintained at a nearly maximum optical output by continuing the aforementioned operations.
FIG. 6 is a block diagram illustrating the structure of a conventional temperature control device for a wavelength conversion device (a potassium titanyl phosphate (KTiOPO4): KTP crystal) which is described in Japanese Patent Laid-open Publication No. 10-20351. The structure thereof will be described, in brief. The signal processing apparatus is constituted by a temperature controller 11 which determines the difference between a commanded temperature and a detected temperature from a temperature detector 5 and outputs an appropriate amount of control for driving a heating/cooling unit 12, the heating/cooling unit 12 which, using the output therefrom, heats and cools the KTP crystal 71, the temperature detector 5 which detects the temperature of the KTP crystal 71, a set-temperature control block 72 for changing the set temperature, and an adder 4 which adds the output from the block to a target temperature. The set-temperature control block 72 repeatedly performs operations for outputting a temperature by which the target temperature should be changed, adding it to the target temperature to change the target temperature, detecting the optical output at the time and comparing the optical output for searching for a temperature which maximizes the light and for setting the temperature as an optimum temperature. Further, these operations are continued for continuously maintaining the optical output at a nearly maximum optical output.